Packaging of adhesives and sealants in syringes is more difficult than in tubes or bottles because of the necessity to provide a dynamic seal between the interior surface of the syringe barrel or tube and the circumferential periphery of the plunger of the syringe forcing the contents from the barrel. This interior peripheral seal must be effective to prevent egress of volatile solvents as well as ingress of atmospheric elements and yet readily permit the plunger to move past the interior wall surfaces of the barrel during the dispensing operation. Failure to have an adequate seal can cause deterioration of the adhesive or sealant properties, premature gelling, and short shelf-life, as well as failure or non-functioning of the applicator.
A particularly difficult class of adhesive and sealant materials comprise reactive compositions and in particular moisture-sensitive or reactive compositions. Cyanoacrylate adhesives and sealants, for instance, polymerize spontaneously in the presence of trace amounts of water, whereby setting or hardening occurs within a few seconds after exposure, particularly in small gaps such as might occur between the interior surface of the syringe barrel and the circumferential periphery of the plunger. A prior art container of cyanoacrylic ester adhesive is shown in U.S. Pat. No. 3,524,537. Prior to the present invention, useful plunger-type syringes did not exist for use in dispensing cyanoacrylate adhesives. A major practical problem relates to internal adhesion and binding between the plunger and interior sidewall of the barrel due to some curing of the adhesive. Similarly, other adhesive compositions, such as moisture-cure polyurethanes and silicones, require moisture-free, sealed syringes operative to dispense the adhesive and yet maintain the adhesive contents remaining in the barrel free of moisture and other atmospheric contaminants.